Re: [PATCH v2 5/5] dax: handle media errors in dax_do_io

Jeff Moyer
2016-04-15T16:11:45Z

Vishal Verma <vishal.l.verma@intel.com> writes:

> dax_do_io (called for read() or write() for a dax file system) may fail
> in the presence of bad blocks or media errors. Since we expect that a
> write should clear media errors on nvdimms, make dax_do_io fall back to
> the direct_IO path, which will send down a bio to the driver, which can
> then attempt to clear the error.

[snip]

> + if (IS_DAX(inode)) {
> + ret = dax_do_io(iocb, inode, iter, offset, blkdev_get_block,
> NULL, DIO_SKIP_DIO_COUNT);
> - return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset,
> + if (ret == -EIO && (iov_iter_rw(iter) == WRITE))
> + ret_saved = ret;
> + else
> + return ret;
> + }
> +
> + ret = __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset,
> blkdev_get_block, NULL, NULL,
> DIO_SKIP_DIO_COUNT);
> + if (ret < 0 && ret_saved)
> + return ret_saved;
> +

Hmm, did you just break async DIO? I think you did! :)
__blockdev_direct_IO can return -EIOCBQUEUED, and you've now turned that
into -EIO. Really, I don't see a reason to save that first -EIO. The
same applies to all instances in this patch.

Cheers,
Jeff

> + return ret;
> }
>
> int __sync_blockdev(struct block_device *bdev, int wait)
> diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
> index 824f249..64792c6 100644
> --- a/fs/ext2/inode.c
> +++ b/fs/ext2/inode.c
> @@ -859,14 +859,22 @@ ext2_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
> struct address_space *mapping = file->f_mapping;
> struct inode *inode = mapping->host;
> size_t count = iov_iter_count(iter);
> - ssize_t ret;
> + ssize_t ret, ret_saved = 0;
>
> - if (IS_DAX(inode))
> - ret = dax_do_io(iocb, inode, iter, offset, ext2_get_block, NULL,
> - DIO_LOCKING);
> - else
> - ret = blockdev_direct_IO(iocb, inode, iter, offset,
> - ext2_get_block);
> + if (IS_DAX(inode)) {
> + ret = dax_do_io(iocb, inode, iter, offset, ext2_get_block,
> + NULL, DIO_LOCKING | DIO_SKIP_HOLES);
> + if (ret == -EIO && iov_iter_rw(iter) == WRITE)
> + ret_saved = ret;
> + else
> + goto out;
> + }
> +
> + ret = blockdev_direct_IO(iocb, inode, iter, offset, ext2_get_block);
> + if (ret < 0 && ret_saved)
> + ret = ret_saved;
> +
> + out:
> if (ret < 0 && iov_iter_rw(iter) == WRITE)
> ext2_write_failed(mapping, offset + count);
> return ret;
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 3027fa6..798f341 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -716,14 +716,22 @@ retry:
> NULL, NULL, 0);
> inode_dio_end(inode);
> } else {
> + ssize_t ret_saved = 0;
> +
> locked:
> - if (IS_DAX(inode))
> + if (IS_DAX(inode)) {
> ret = dax_do_io(iocb, inode, iter, offset,
> ext4_dio_get_block, NULL, DIO_LOCKING);
> - else
> - ret = blockdev_direct_IO(iocb, inode, iter, offset,
> - ext4_dio_get_block);
> -
> + if (ret == -EIO && iov_iter_rw(iter) == WRITE)
> + ret_saved = ret;
> + else
> + goto skip_dio;
> + }
> + ret = blockdev_direct_IO(iocb, inode, iter, offset,
> + ext4_get_block);
> + if (ret < 0 && ret_saved)
> + ret = ret_saved;
> +skip_dio:
> if (unlikely(iov_iter_rw(iter) == WRITE && ret < 0)) {
> loff_t isize = i_size_read(inode);
> loff_t end = offset + count;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index dab84a2..27f07c2 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3341,7 +3341,7 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
> {
> struct file *file = iocb->ki_filp;
> struct inode *inode = file->f_mapping->host;
> - ssize_t ret;
> + ssize_t ret, ret_saved = 0;
> size_t count = iov_iter_count(iter);
> int overwrite = 0;
> get_block_t *get_block_func = NULL;
> @@ -3401,15 +3401,22 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
> #ifdef CONFIG_EXT4_FS_ENCRYPTION
> BUG_ON(ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode));
> #endif
> - if (IS_DAX(inode))
> + if (IS_DAX(inode)) {
> ret = dax_do_io(iocb, inode, iter, offset, get_block_func,
> ext4_end_io_dio, dio_flags);
> - else
> - ret = __blockdev_direct_IO(iocb, inode,
> - inode->i_sb->s_bdev, iter, offset,
> - get_block_func,
> - ext4_end_io_dio, NULL, dio_flags);
> + if (ret == -EIO && iov_iter_rw(iter) == WRITE)
> + ret_saved = ret;
> + else
> + goto skip_dio;
> + }
>
> + ret = __blockdev_direct_IO(iocb, inode,
> + inode->i_sb->s_bdev, iter, offset,
> + get_block_func,
> + ext4_end_io_dio, NULL, dio_flags);
> + if (ret < 0 && ret_saved)
> + ret = ret_saved;
> + skip_dio:
> if (ret > 0 && !overwrite && ext4_test_inode_state(inode,
> EXT4_STATE_DIO_UNWRITTEN)) {
> int err;
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index d445a64..7cfcf86 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1413,6 +1413,7 @@ xfs_vm_direct_IO(
> dio_iodone_t *endio = NULL;
> int flags = 0;
> struct block_device *bdev;
> + ssize_t ret, ret_saved = 0;
>
> if (iov_iter_rw(iter) == WRITE) {
> endio = xfs_end_io_direct_write;
> @@ -1420,13 +1421,22 @@ xfs_vm_direct_IO(
> }
>
> if (IS_DAX(inode)) {
> - return dax_do_io(iocb, inode, iter, offset,
> + ret = dax_do_io(iocb, inode, iter, offset,
> xfs_get_blocks_direct, endio, 0);
> + if (ret == -EIO && iov_iter_rw(iter) == WRITE)
> + ret_saved = ret;
> + else
> + return ret;
> }
>
> bdev = xfs_find_bdev_for_inode(inode);
> - return __blockdev_direct_IO(iocb, inode, bdev, iter, offset,
> + ret = __blockdev_direct_IO(iocb, inode, bdev, iter, offset,
> xfs_get_blocks_direct, endio, NULL, flags);
> +
> + if (ret < 0 && ret_saved)
> + ret = ret_saved;
> +
> + return ret;
> }
>
> /*